    * {
      box-sizing: border-box;
    }

    body {
      margin: 0;
      font-family: Arial, sans-serif;
      display: flex;
      background-color: #f0f0f0;
      height: 100vh;
      overflow: hidden;
    }

    .container {
      display: flex;
      width: 100%;
      height: 100vh;
      overflow: hidden;
    }

    .sidebar {
      width: 250px;
      background-color: #fff;
      padding: 20px;
      box-shadow: 2px 0 5px rgba(0, 0, 0, 0.1);
      overflow-y: auto;
      border-right: 1px solid #ddd; /* 阴影分界线 */
      display: flex;
      flex-direction: column;
      justify-content: space-between; /* 将内容与按钮分开 */
    }

    .sidebar h2 {
      font-size: 18px;
      margin-bottom: 10px;
      color: #333;
    }

    .sidebar ul {
      list-style-type: none;
      padding: 0;
      flex-grow: 1; /* 使目录部分扩展，保持返回按钮在底部 */
    }

    .sidebar ul li {
      margin: 15px 0;
    }

    .sidebar ul li a {
      color: #333;
      text-decoration: none;
      cursor: pointer;
      display: block;
      padding: 8px;
      border-radius: 4px;
    }

    .sidebar ul li a:hover, .sidebar ul li a.active {
      background-color: #e0e0e0; /* 悬停时背景色加深 */
    }

    .back-button {
      padding: 10px;
      background-color: #007bff;
      color: #fff;
      border: none;
      border-radius: 4px;
      text-align: center;
      cursor: pointer;
      margin-top: 20px;
      text-decoration: none;
      display: block;
    }

    .back-button:hover {
      background-color: #0056b3;
    }

    .content {
      flex: 1;
      padding: 40px;
      overflow-y: auto;
      overflow-x: hidden; /* 禁止左右滚动 */
      background-color: #fff;
      text-align: left;
      padding-left: 300px;
      padding-right: 300px;
    }

    .content h1 {
      font-size: 24px;
      color: #333;
      margin-bottom: 20px;
      text-align: left;
    }

    .content h2 {
      font-size: 20px;
      color: #333;
      margin-top: 20px;
      text-align: left;
    }

    .content p {
      color: #555;
      line-height: 1.6;
      font-size: large;
      text-align: left;
    }